The piezoresistive effect has been widely employed in the fabrication of semiconductor transducers for various applications. Essentially, such transducers utilize a monolithic, integrated circuit Wheatstone bridge formed directly on a silicon diaphragm by solid state diffusion techniques. The prior art fabricates such transducers from many various semiconductor techniques which are used and employed in the integrated circuit art. Essentially, there are two main methods for obtaining an isolated sensor network on a monolithic body. One technique employs PN junction isolation utilizing solid state diffusion and oxide masking. The other technique employs dielectric isolation using silicon dioxide as the dielectric and epitaxially grown silicon as the monolithic structure. Basically, such techniques have been widely employed and both have their inherent advantages and disadvantages. For an example of a technique using PN junction isolation reference is made to U.S. Pat. No. 3,654,579 entitled Electromechanical Transducer and Housing, issued on Apr. 4, 1972 to A. D. Kurtz, et al and assigned to the assignee herein. An example of a structure using dielectric isolation may be had by referring to U.S. Pat. No. 3,800,264 entitled High Temperature Transducer and Housing including Fabrication Methods by A. D. Kurtz, et al and assigned to the assignee herein. As indicated in the above patents as well as many additional patents, there are many configurations and structures which operate with the piezoresistive effect to provide measurements of pressure or forces subjected on a diaphragm or other device associated with the transducer.
It is a primary objective of the present invention to provide a transducer apparatus which operates with the piezoresistive effect but which does not require the fabrication of separate resistive devices. Accordingly, the present invention eliminates many processing steps which are normally employed to fabricate transducers according to the prior art and of the types and kinds indicated above.